We are continuing to test the hypothesis that the ratio among the concentrations of the adenine nucleotides, expressed as the adenylate energy charge (the mole fraction of ATP plus half the mole fraction of ADP) is a fundamental parameter in the correlation and control of metabolic sequences. We are studying regulation of the transfer of phosphoryl groups (in effect, of metabolic energy) from ATP to nucleoside diphosphates, a reaction that we think may play a central role in the regulation of macromolecular synthesis. We are looking at control of synthesis and degradation of adenine nucleotides and, in a mutant incapable of synthesizing adenylates, at the interrelation between the size of the adenylate pool and the value of the adenylate energy charge.